Semi-automatic telephone system



G. E. MUELLER.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED N,0V.16, 1907.

1,391,135. Patentedsept. 20,1921.

, 6 SHEETS-SHEEI 1.

G. E. MUELLER.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED NOV. 16, 1907.

1,39 1 1 35, Patented Sept. 20, 1921.

6 SHEETSSHEEI 2.

G. E. MUELLER.

' SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED NOV. I6, I907- I I PatentedSept. 20, 1921.

6 SHEETS-SHEET 3.

G. E. MUELLER.

SEMI-AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED NOV. 16, 1907.

1,391,135, PatentedSept. 20, 1921.-

6 SHEETS-SHEEI 4.

e. E. MUELLER.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

. APPLICATION FILED NOV-16,1907- I 1,391,135, PatentedSept. 20,1921.

G. E. MUELLER. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION EILED NOV. 16. 1907. Q

PatentedSept. 20, 1921.

6 SHEETS- SHEET 6.

l "0 all whom itm'ayconcern UNITED STATES",

PATENT. cl rics,

GEORGE E. MIiELLER, or AURORA, ILLINoIs, ASSIGNOR, BY ,mnsn'n assmmnms, "'ro KELLOGGSWITCHBOARD & SUPPLY COMPANY, n-conronArIoN'onaIm-mom.

- :snmI-AuroimArIo rELEPIIonELsYsrEu.

Be it known that 'I, GEORGE E. MUELLER, residing in Aurora, inthe county'of Kane andState of Illinois, have invented new and useful. Improvements in Semi-Automatic Telephone Systems, of which the following is a specification.

My invention relates to 'asystem in which the substations are provided 'with'telephonic outfits similar to those customar'ily used' in manual telephone" practice, electro-magnetically controlled mechanism being'employed at the exchange to interchangeably connect calling subscriber's lines with idle operators positions, the incoming calls being automatically distributed -to' the different positions of the switchboard according as they are idle or busy. When a calling line has been connected to anfidle operators position, a suitable signal is displayed and the operator, having thereupon ascertained in the usual manner the want of the subscriber, completes the connection fi'to the called line by operating a suitably arranged impulse controlling device whichjactuates directively operable selective switches in a,

automatic telephone practice. Each submanner generally similar to that employed in automatic telephone practice.

One of the objects of the present invention is 'to provide'arelatively simple means for distributing the incoming calls, which I accomplis'h'by means of selective switches less in number than the number of "calling lines. The switches for this purpose are preferably arranged in permanently associated pairs and for each initiated call, .a pair of switches is set into-actuation, one. of which will select the calling line while the other will select a link-circuit at an idle operatorls position. Another object offthe invention is to provide a structure wherein all'the' switches'used 1n the connect on are restored 'to then normal posltion'as soon as the two subscribershave replaced their, re-

ceivers,'although the scope of-the invention is notflimited to this precisearrangement. Other objects of the invention are foundin certain details of arrangement and mechanism which will 'be more particularly pointed out in the detaileddescription and the claims.

Referrlng to the drawings, Parts 1, 2 and 3 of Figure 1 when arranged in consecutive order with Part 4 above Part 2, illustrate a preferred circuit arrangement embodying provided with multiple called contacts "13, "14, 15,, appearing in-the "banks of a suitable Specification ofLcttersPatent, P t t dg h 29, 192

Application filed November .16, 1907. Serial No. 402,413. 7

the invention. "Fig. 1 illustrates 'a plane view of -an operators "in'ipulse trans initting key-board; Fig. ;2 illustrates a circuitar rangement adapted, tobe inserted between Parts'2 and '3 of Fig. 1, whereby interconnection of two distanteirchanges may "be accomplished bykthe use of ajpair of conductors only Fig. 3 is a left elevation of a selective switch that may .be employed ,in connecting circuits, the contact bank being. shown in section, whileI-Fig. Jc'is a front elevationthereof, and Fig. 51is.a right elevation thereof. Fig. 6 showsthe off-normal switch combination of the mechanism of Figs. 3 to 5. Fig. 7 is a sectional View on line XY of "Fig. "4. showing'the arrangement of the primary magnet PM with relation to the switch shafts. Referring -first te Fig. 1, I show at a subscriber.s telephone station-including the :hook lever 1,

controlling in the usual mannerythe signal.- 7

' ing and talking circuits of line limbs 2-93,

which extend to theexchange and are there number of connectors as is customary in scribers line is also provided "withmultiple calling contacts '28, 30,132, indivi dual to the line, which are multiplied .at the banks of a suitable number of line selectors, the

circuits of one, of which are shown at "C.

.These -line selectors "have'the wipers 27,29,

31, of which 27 is the so-called private preferably'has linked with it .a trunk se- 'lector D be'fore'whose wipers- 52, 54, "56,

appear multiple contacts '53, 55, 57,015 a; number of link-circuits "E extendingito diifferent operators positions, each link-circuit being preferably provided with an impulse transmitting switch of the character shown inFig. 1 Part 4,. although the invention is not limited to this specificarrangement. Each link-circuit E is also provided with a call signal 90 and supervisory signal 91 together with the'listening key levers 92 and 93 serving, when "actuated, to connect the operators telephone set with the link-circuit.

* Each link-circuit also has preferably 'a first or thousands selector F responslve'to the operators impulse transmitting mechanism to select a group of second orhun 'dreds selectors H and then an idle selector of the group, the second selectors being" assigned for connections tor the different thousands of the exchange, by groups, ac-

cording to the well known automatic tele phone practice. The second selectors H are operable responsive to the impulse transmitting mechanism to select a desired group of connectors and then an idle connector, the

connectors being assigned in groups for connections to each hundred of the thou-- sands which thesecond selector serves, in the well known manner. Each connector will have before it multiple terminals of one hundred subscribers lines and each con-- SS terminals of the wanted line'out of'the selected group.

The mechanism illustrated in Figs. 3 to 7 is specifically that of the line selector at C in F i 1,, and comprises theadjustable' wipers 27, 29, 31, beforewhich are arranged one hundred sets of individual terminals 30, 28, 32, arranged in ten groups of ten contacts sets each. Fig. 4, showing best the arrangement of these groups as a whole, haseach' contact set 30, 28, 32, represented by a single short line. In Fig. 3, the ten sets of contacts 30, 28, 32, constitute a group.

It will be apparent from an inspection of Figs. 3 and 4 that the contacts are arranged as though projecting through the inner surface of a section of a sphere. In order-to select a group of contacts, the'wipers 27, '29, 31, will accordingly be rotate'd'from left wipers are pivotally attached to the primary shaft PS, which is suitably journaled to the main frame of the switch and which also hasattached to it therotary ratchet 300 (Fig. 7), which is adapted to be actuated step-by-step in a rotary clock-wise direction by the pawl 303 controlled by the armature of primary magnet PM. .Thus, when sucstep the ratchet 300 and shaft PS and wipers 29, 27, 31, step-by-step, the said .wipers, with each step, being brought immediately beneath a different vertically disposed group of contacts 30, 28, .32. This rotary stepping is against the tension-of the spring 302, one end of which maybe at tached to the frame of the switch and the other to the shaft PS, the retaining pawl them about the pivot 305, a secondary shaft SS is provided, having at its lower extremity a'suitable piece 306, interlocking suitable antl-frlction bearing at the eX- tremity of the wipers distant from the con-.

tact bank, said piece 306, as shown in Fig.

4,'being sufficiently broad that when ;the

wipers are primarily adjusted, theirdistant ends cannot be rotated far enough todis-Q engage said piece 306. The secondary shaftpasses through the upper and lower plates of the main frame and has the ratchet V 307 adapted to be engaged by the pawl309 carried by the armature 319' of secondary magnet S successive actuations" of said secondary magnet SM effecting, by pawl- 309, successful downward steps of shaft SS each such downward step rotatingthe ends move step-by-step upward over the contact sets of the selected group. 7 As shown wipers about pivot 305 so that their contact in Fig. 5, a suitable pivotally supported y lever 312 engages loosely by its longer arm a screw insertedin secondary sha"t SS, the;

shorter arm of said lever 312 being held under tension by a restoring spring 313 so that the tension of said spring resists the downward movements of the shaft SS- To 1 V prevent back movements under the influence of the said spring, the secondary retaining pawl 310 is providedengaging the ratchet 308 of the shaft SS, as shown in Fig. 4.

As when the'magnets PM and SM are inert, their respective pawls 303, 309 are,

spring 313 will exert itstensionto-restore the secondary shaft SS. 1 To accomplish these withdrawals, a release magnet RM is provided havingiits armature 318 arranged to engage an extension 317 ofthe pivoted pawl 304, as shown in Figs. 7 V and 5. Thus,- when the magnet RM is energized, the arvmature 318 engages the piece 317 and rotates pawl 304 free of ratchet 300. Asthc said pawl 304 interlocks 'with the spring,

arm 314 attached to the secondary retaining pawl 310, asshown in Figs. 4 and 5', the

rotation of pawl 304 is effective to withdraw the pawl 310 so that the secondary shaft may be restored under the influence of In order to prevent frictionspring 313. of the wlpers upon thecontacts of the selected group while the secondary shaft is being restored by spring 313, an arm'3l6 is provided extending through the upper and lower plates of the main switch frame, the said arm being normallyheld in the position shown in Fig. 5"by the piece 316* attached ,to the shaft SS. As soon, however, as the first downward step ofthe shaft SS is effectdescent, the pawl 311 of piece 316 engages whatever toothof-fthe ratchet 300 hasbeen brought opposite to it by the primary stepping of the switch so that the primary shaft PS is locked in its rotated position. Thus, while the secondary shaft SS is being restored upward, the pawl 311 holds the primary shaft, although retaining pawl 304 has been withdrawn from ratchet 30 0. As

the shaft SS reaches its'normal position, piece 316* engages piece 316 and lifts pawl 311 free from ratchet 300, when spring 302 is effective to bring the primary shaft PS back to its normal position. It will be seen that the return movements of shaft SS is limited by piece 316 engaging the lower surface of the main switch frame. The return movement of primary shaft PS is limited by the arm 301 fastened to said shaft, as shown in Fig. 6 engaging its associated pin projecting from the top surfaceof the switch frame.

From the description given, it is apparent that the primary off-normal springs PO shown in Fig. 6 are allowed to shift by their tension to assume their alternate positions on the first primar step of shaft PS, stud 301 fastened to sha t PS, moving free of spring PO, and are restored when said shaft reaches normal. The secondary off-normal switch springs SO, whose mechanism is best illustrated in Figs. 4 and 5, are controlled by the piece 316, being shifted on the first second ary movement of shaft SS and being restored as soon as the shaft reaches normal.

It will of course be understood that the armatures of the various magnets areprovided with suitable restoring springs and that the pawls have the usual pivot springs.

Various minor mechanical details of the switch mechanism are apparent from an inspection of the drawings and a minute specifying of them is considered unnecessary to a. full understanding of the mechanical figures which it will be understood are diagrammatic to a certain extent.

For the line selector, the group of ten horizontally disposed contacts 34 is provided with which the wiper 33 engages, said wiper engaging a different contact 34 with each primary step of shaft PS. It is apparent that the wiper 33, while partaking of the primary movements of the switch, does not partake of the secondary movements, but will remain engaging whatever contact 34 it may bebrought to engage by the operation of shaft PS.

Referring now, to Fig.1, a telephone system organized in accordance with the invention may comprise, as a whole, a number of subscribers" lines extending to substations such as A or K, said lines at the exchange being divided into groups of one hundred, as

calling lines, the multiple calling terminals 28, 30, 32, of each group appearing in the banks of a number ofline selectors C of whichten may be sufiicient for each group of one hundred lines. At the line selectors the line terminals. 28, 30, 32, will be arranged in sub-groups often contact sets each, and for each sub-group there will be provided a' group contact 34, located as described, in

connection with the mechanical drawings. The wipers 27, 29, 31, set in travel when acall is initiated over a line ofa group, are controlled in their primary movements to select the sub-group-of contact sets, including that of the calling line, by'the group wiper 33 engaging the group contacts 34 succes sively' until one is found in an abnormal electrical condition, this condition having been caused by the removal of the receiver at the calling substation. Thereupon the line wipers 27, 29, 31, commence their secondary movements up over the contact sets'of the sub-group of lines until they reach the contacts of the calling line. V

The removal of a receiver at a calling substation not only starts into operation an idle line selector C to select the calling line, but

also starts simultaneously, a trunk sele'ctorD whose wipers 52, 54,56, 58, coiiperate with the contacts 53, 55, 59, to select an idle link, or trunk circuit E at some operators position. The operators'circuits E are preferably arranged in groups of one hundred, having multiple contacts 53, 55, 57, appearing in the banks of a number of trunk selectors D. These multiple contact sets are group contacts 34 in their electrical characteristics, being normally selectable-by the group wiper 58, the arrangement being such that the wiper 58 will stopengaging any contact 59 in its normal condition, the said contacts 59 being rendered unselectable only when all the operatorss trunk circuits E of their respective sub-groups have been selected by trunk selectors D.

Of course the operators circuit E need be in number only a small percentage of the:

number of lines in the exchange as is usual 1n strictly manual telephone practice, ten per cent. being an ordinaryproportion of operators circuits. Thus, in a ten thousand line" exchange, one thousand operators circuitsE would be expected to besufficient tohandle the maximumtraflic. As the trunk selectors D are preferably similar to the line selector already described, each containmg one hun- 7 line selectors are to serve one hundred subthere would be ten such groups of one'thonone hundred operators circuits. 7 case, thefirst sub-group of operators circuits.

scribers lines, and therefore, the multiple contacts 53, 5 5, 57 of each group ofoperators trunks would be multipled before one hundred trunk selectors D connected by tens with the respective line selectors (l of ten one-hundred-line line groups. I

It is thus apparent that one thousand lines may have-access'to a common group of' one hundred operators circuits, and in the ten thousand line exchange supposed,

sand lines each, each group having access to a particular one hundred operatorscircuitsE'.. I

In distributing the operators circuits E amongthe diiferent operators, any of a variety of arrangements may be employed-,

it being assumed in the present description that each operator is able to handle proficiently ten operaors circuits, E. -One arrangement would be to have a dliferent group of ten operators for each group of In this would preferably be assigned to afirst operator, a second subgroup of circuits to a second operator, and so on for the ten sub-groups of the one hundred operators circuits E serving a one thousand line group of subscribers, and a similar arrangement could be made with respect to the other group. of operators circuits for the other thousands. By this means, the first ten calls of any line group would be concentrated before a first operator. As soon as more than ten co-existing calls existed, the additional ones would be distributed to the second operator, and when more than twenty calls co-existed, the additional ones would be As before mentioned, tengiven to the-third operator, andso on to the other operators-positions. Another arrangement that'migl'it be satisfactorily employed 1 Would be to have a first operator have be jfOI her thefirst circuit :E of the first sub-, group ofeaoh one-hundred group. of operators circuits, there being "ten such "groups,

and therefore ten cords before this first operator. Therefore there would reachthis first operators position, the first call from each of theone-thousand-line line'groups'.

The second operator would have thesecond operators circuits of the first subgroup of each one-hundred circuit group, and so on up -until the tenth operator would have the tenth circuits of the first sub-groups. The

eleventh operatorwouldhavefthe firstcireuits of the secondsub-groups, and so on to the other sub-groups.

It is obvious that other assignments ofoperators"circuits might -be'made with the 7 same general object in view of concentratingthe calls at onexendof the board, or before certain operators." For instance, there are many combinations intermediate of the two morespecifieally before referred to that might be employed.

As called lines, the subscribers lines are divided into groups of one hundred, according to the directory numbers assigned to the different subscribers 7 stations. Each group or one hundred group lineshas in addition to its calling multiple terminals 28, 30, 32 before described, called multiple terminals 13,14,15, appearing in the banks of a suitable number of connectors I. In

ordinary practice, ten such connectors for each one hundredline groupswould be adequate, the subscribers lines at the connec tors I being divided into'ten sub-groups, the operation of the connector being first directively controlled to select the sub-groupofcontact sets containing terminals of the desired; line, .and then directively adjusted overthe'contact. sets of the sub-group to find the contacts forming individual terminals of the wanted subseribers line.

' The connectors I, by their terminals 143,

144, 145', are divided into groups according to the thousands which they serve, the connectors serving each one hundred of the one thousand having their. terminals 143, 144, 145, appearing as asub-group of contact sets in the banks of a suitable number of 7 second, or hundreds, selectors H which are directively adjusted to select the sub-group of contacts forming theterminals of the wantedconnect-ors, the second selector being then automatically adjusted to select arr.

idle connector of the selected sub-group. The second, or hundreds selectors H have their multiple terminals '130, 131, 132, ar-f ranged in sub-groups before first, or'thou--.-

sands, selectors F, second selectorsH of each different one thousand having their terminals appearing as a sub-group before the wipers 96, 97, 98, of first selectors F, it

being understood that the first selectors F with their wipers 96, 97 98, constitute the outgoing end of the Operators circuits E,

in which the'operators talking set isc'a-used to be connected with the different cords at will.

I will now briefly describe the impulse transmitting mechanism illustrated at E in *ig. 1. The arrangement illustrated at E is capable of transmitting five sets of current impulses, springs a having the exponents prime, square, cube, etc, being for transmitting the ten thousands digits, wlth springs b for transmitting the thousands digits, the springs 0 for transmitting the hundreds digits, the springs cl'for the tens digits, and the springs e for the units digits. It will be understood of course, that in the ten thousand line system, the numbers would all be four digit numbers,- the' highest numbered line being line 9999, so that the device at E actually provides for the transmission of one digit more than would be required for the system heretoforespecifically referred to. y p

' Each of these springs a, a etc;, will have its actuating button 129 arranged in a linear group, as shown in Fig. 1*. When a button 129 isdepressed, it will remain inits 'depressed condition holding its respective spring a engaging the associated grounded contact. When however, some other button 129 is depressed, a previously actuated one will be automatically restored to its normal position in a well known manne1-,th-is being similar to the ordinary well known arrangement'used in four p'arty line manual ringing practice as exemplified in patentto Setter, No. 799,019, dated-September 5, 1905. Similarly, the buttons 128,- one being provided for each spring 6-, are arranged ina linear group, as shown in Figll and the same is true of the"buttons 127 for the springs 0, the'buttons12 6' forthe springs d, and the buttons 1'25' for" for the springs e. With reference to the buttons 125, each of these has associated with it an additional spring f, arranged to be? actuated when a button is depressed to close contact to ground, the arrangement being such that when a button 125 is thereafter'relea'sed, it will be raised sufficiently to allow the? spring f disengage its. con ract, but not sum ciently to" allow the spring a to disengage" its= contact The springs f are only required to make a momentary "contact to initiate "travel of the rotary switch sliaft 1 -00 The exponents of' the springs a, 6,0, d, a nd'e,.indicate the number of impurses-eac 'springis effective to cause the transmission of when actuated itbein underst'ood that 'for a complete system, as indicated-in Fig. 1?, there would be ten buttons 129; onefor each digit, and consequently ten springs a, and so o'ntfor thev other springs and buttons.

To exenipli-fy the employment of the impulsetransmitter E, letit be assumed that the mnn-ber'33,333 is to be transmitted. The

operator will actuate the keys suitable to cause the grounding of springs a 6 0 (Z and c thus grounding the middle contacts 1193-120, 121-, 122 and 123', which are circularly arranged for engagement by the wiper 118 carried bythe shaft 100 to which are also fastened -t he wiper 117 and the ratchet 101. The impulse. transmitter proper is; a

step-by aw "switch comprisingjthe shaft 1*00,-the magnet MM byits associated armature control led; pawl being arranged to drive the ratchet IOI 'carrying with it the" shaft 100, the notched disk 1 02 and the wipers} 117 1 1 8,-"circuit connections being provided, aster-carter specified, to cause the magnet to actuateits pawl to effect-a complete rotation of the shaft each time the impulse of the arrow, whereby the stud of insulating 'm'a'terial upon disk 102 is brought to free spring 109, and said spring 109 and spring 66' assume their alternate positions. Thus,

when the armature of relay 116 is retracted net and a rotary step of ratchet and shaft.

Interru-pter V will continue totransmit impulses until a complete revolution of shaft and ratch t hasbeen effected, when the stud of insulating material will again engage the spring I09and1ift it free of its conta'ct,f

wh n the pening of the ircuit of magnet MM will cause the'switch to come to rest, spring 66 beingsimultaneously shifted to n ma r r 110 is a grounded ring of conducting-material having five sets of projections 111, 112,

r 113, 114, 115.. AS the shaft 100 is rotated by .magnet MM, the wiper 117 will obviously rotate over thecontacts 111, ll2,etc., said wiper beingconnected to ground once for.

each projection engaged by it. 94 is'a con ductor over which the directive impulses are transmitted to the mechanism of the operato'rscircuitE. It is obvious, however, that until the relay 99 is energized, the engageinent of wiper .117 with the grounded project-ions in ineffective to transmit impulses over conductor 94," but that as soonas relay 99 is operated, the wiper 117 will transmit as many impulses overv 94 as it thereafter engages projections, while relay 99 is held energized. It is-also evident that one. Relay 99,.when operated, locks itself to ground at spring lO8 and will continue in the energization of relay '99 is dependent 'upon the engagement ofwiper 118 with a grounded one .of its contacts119 or 120, etc. Thus with the travel of ratchet 101 and shaft 100, impulses will begin to be transmitted by wiper 117 over conductor 94 as soon as wiper 1'18 engages a grounded contact 119.

The actuation of spring a previously described, having grounded the middle'contact 119, relay 99 will'bej operated'when wiper 118 engages saidcontact from-ground at spring a through middle contact 119, wiper 118, the said relay 99 to battery B .whereon wiper 117having traveled coincidently with wiper 118' will transmit three impulses over conductor 94, one impulse from ground at the middle projection 111, and two other'impulses whenit engages the two projections at the right of the middle its locked condition until the spring 108 en- .gages the notch 103 which notch will be brought opposite the said spring 108 when wiper 117 passes beyond the last contact 111. WVhen spring 108- engages notch 103,

' it opens the locking-circuit of relay 99 and,

;It is apparent that with the continued rota- 'tion of the shaft 100, another set of impulses will begin to be'transmitted through the projections 112 and'wiper 117 as-soon as wiper ,118 engagesa grounded contact 120 to cause the energization and locking of relay 99, the impulses transmitted being followed by a single impulse over conductor 95 by engagement of spring 108. with notch-104, and that mitt d by means of the projections 113, 114,

additional'sets f impulses will betrans- 115, as wiper 11s engages Contact 121,122, 123, each set of impulses being followed by one over conductor 95 as spring 108 engages the respective notches105, 106,107. lnjthe case supposed, in which .the middle contacts 121, 122-, 123, were grounded, each set will obviously consist of three impulses'over con- .ductor 94 followed byione over conductor 95 the switch being stopped as before described, when-it completes a revolution.

' For convenience of the drawing, the offnormal'sprin bo and its contact are shown.

both at Ein Fig; 1, Part 2, in its electrical association and also at E in Fig. 1, Part 4, mechanically connected with spring 109, its

electrical connection in the latter case being omitted. r

Assumin that subscriber A desires his line to be connected with that of the subs 'scribers line K whose telephone number is 'assumedto be 3333, the subscriber at A re-' moves his receiver, whereupon hook-lever 1 engages ts upper contacts thereby complet-' ing a conduct ve bridge of line limbs 2- and 3 to produce 'aflow of current frombatt'er B through normal contact 12 over the "lim 3', hook-lever 1, limb 2, normal contact 9, line relay 4 to ground-,said relayiattracting its armatures V and locking itself through alter- ,nate contact 7', normalicontact 11, relay 17 of master-switch-mechanism BB to battery B." Attracted armature 6 'places ground I uponthe private multiples13 at the connectors, rendering line A busy against in-' coming calls. Armature- 5 energizes the group relay 16 by grounding the common conductor 16 which has a branch to all the line relays4 of the lines of the sub-group among which'A is included. {The attracted armature of relay 16 removes ground from. the second set of a multiple group-contacts V 34 1 to render the group selectable by the group private -\viper33. 'Attracted armature 5 also removes ground from the multi ple privatecontact 28,28 of the line of A at the line selectors torender the same se-f V lec'table by the private wiper 27.

D, and 24 for switch C, and the contact 26 at the master-switch mechanism BB, the wipers 21 23, 25, being arranged to succes sively engage the contactsets 22,24, 26 of the different switch pairs I No mechanical illustration Each pair of switches CD, serving-the one 1 hundred lines among which A'is included, have their respective contacts 22, for switch V v of the masterswitch is considered necessary for an understanding of the case,'the said switchbeing preferably a rotary device having-the wipers 21, 23, 25, mounted upon arotary shaft in the same 1 direction.

drivenjby a magnet M, travel being always The wipers 21, 23, 25, normally rest en gaging contacts 22,24,- 26, of anidle switch --pair' CD, the r c n rol bei g hereafter de net PM by current'from generator scribed. By the energization of the relay 17, effected by current transmitted over the common conductor 17 (which has a branch to each armature 7 ofthe line relays'4 of r the one-hundredline group of lines among whichA is included), thearmatures' 18 and 19 were attracted to close circuits from ground through armature 20, said armatures 1'8 and 19., contacts 2 1 -22 and 23-24, re

spectively.

The grounding of contact 24 energizes primary relay PR whose attracted upper armature'causes actuations' of primar magsaid magnet stepping. the Wipers :33, 31,- 29, 27, on their primary movements. The lower armature of relay PR connected the relays winding from battery B to the group private wiper 33, said wiper engaging successive contacts34 and establishing. successive looking circuits for relay PR to ground at armatures. of relays 16 until said wiper 33 en- 7 gages a contact 34, whose. group relay 16 has been energized by the initiation of a call over one of the lines of its sub-group. Whenthis occurs,. (the primary off-normal switch springs-PO having been shifted on the first primary step of switch C) the locking-circuit through PR. is broken, the relay delinergized, and the actuations of magnet PM cease on the retraction of the armatures of relay PR. Wiper 33 thus stops, engaging the ungrounded vgroupcontact 34, wipers 27 29,; 31, being-then opposite a group or section of contacts 28, 30, 32, including those of the calling line A.

When relay PR is deener'gized, its upper contact-connects groundthrough the shifted primary off-normal spring PO, secondary off-normal contact S0 with the winding of secondary relay SR and battery B, energizing said relay SR, which attracts its armature whereof 41 connects generator through secondary magnet SM and normal contact 37 with ground, said magnet. SM being successively actuated while relay SR continues energized to step the wipers 27 ,29, 31, up over the line contact sets of the selected sub-group. iArmature of relay SR connects the relays winding through normal contact of magnet RM with the private wiper 27 which wiper moves over the contacts 28 of-the different lines, the contacts of non-calling lines being. grounded through armatures 10 and 5 of their respective line circuits. Thus successive locking circuits for relay SR will be established holding it energized until wiper 27 engages contact 28 of the calling linezA which contact will be ungrounded because .o'fsthe attraction of armature 5 of line relay 4. Secondary offnormal spring SO being shifted with the first secondary step of switch C, relay SR will be de'e' nergized whenlwiper 27 engages the gr unded oontact,= its armatures tracted and the circuit of'magnet SM opened whereby the wipers 27, 29, 31, rest engaging the contacts 28, 30, 32, of the line of A.

The grounding of contact22, before de scribed, extends ground over conductor through normal contact PO, primary relay PR of trunk selector D to battery, energizing said relay PR which, by its left armature, causes magnet PM to effect primary steps of wipers 52, 54, 56, 58, under the influence of generator G, and by its right armature,connects the winding of said relay PR with the group private wiper 58. PO is a primary off-normal switch on the first selector F "connected to the operators circuit E, PO andPO being primary off-normal switches on other first selectors F of operators circuits E, having their contacts in the same sub-group as that circuit shown at E. Thus it will be seen that when all the first selectors F. have been moved off-normal, the

group contact 59 of that sub-group will be grounded through the successive primary off-normal springs P0 P0 P0 etc., of 4 the link selectors of the link-circuits of the sub-group. In this'connectiom it should be observed that branch circuits connecting the successive springs P0 P0 etc, are provided through the armatures 70 of the secondary relays SR of the operators circuits E, and as these relays: SR are held energized from the time a circuit E is selected by a switch D until the first selector F is moved ofi-normal, the electrical condition of thegroup contact 59 has protection from the moment of selection. It is also apparent that unless all the first selectors F of the sub-group are off-normal, or the relays SE of the operators circuits E of a sub-group are energized, the group contact 59 will not be grounded, so that as long as one link-circuit E of a sub-group is idle, the sub-group G contact 59 will be selectable.

PR, byits right-hand or locking armature,

will therefore continue energized, while magnet PM is moving wiper 58 and also the other wipers of switch D two steps. On the second step however, when wiper 58 engages the second contact '59, the circuit of relay PR will be opened and the relayjdeenergized,. its armatures'falling back, the left armature closing the circuit from ground 1 through its normal'contact, shifted contact PO", the contacts PO having been shifted with the first primary movement of the switch D, through the normal secondary offnormal switch contact S0 secondary relay master-switch BB, 7

a The, @WQ SW tChQS having completed SR to battery B energizing relay SR which, by armature 47, completes a circuit for generator G through secondary magnet SM to ground. Said magnet SM, responsive to impulses received, now steps the wipers 52, 54, 56, step-by-stepup over the contact sets 53, 55, 57, of the selected subgroup of the operators circuits E, andas contacts 53, of busy circuits will be grounded, as hereafter explained, relay SR will continue energized (thus keeping closed the c1rc1ut of secondary'magnet SM) over successive locking-circuits extending from battery B relay SR, attracted armature 45, wiper 52, and successive grounded contacts '53 until the said wiper 52 reaches an ungrounded contact assumed to be that operatorscircuit E shown in Fig. 1. Such contact 53 will be ungrounded as an inspec tion of Fig. 1 will show, relay SR will be denergized and its armatures will fall back whereof 47 opens the circuit-of magnet SM preventing the further stepping of the wipers 52, 54, 56, which thus remain engaging the respective contacts 53, 55, 57, of the operators circuit E shown in Fig. 1. Y r

- The secondary off-normal springs SO and S0 of switch C were shifted on the first secondary movement of said switch and the springs SO and S0 of switch D were shifted o the first secondary movement of switchD. Thus, as soon as the two switches C and D have completed their selection, and relays SR and SR are accordingly .deenergized, a circuit will be completed as follows from ground through normal contact 37 switch C, through normal contact-41, contacts SO, S0 now closed, normal contact 46, and over conductor 51 to contact 26 of the swhich pair CD at master-switch BB, through wiper 25, relay R, to battery B, energizing relay R'which attracts its armature 20 to complete a circuit including generator' G, and magnet M of master-switch BB, whichmagnet now receives impulses causing it to step Wipers 21, 23, 25, step-bystep in a rotary direction over the contacts 22, 24, 26;. The contacts 26 pertaining to busy switch pairs will be grounded'through circuits of their respective switch pairs similar to that .just described, wherefore, relay R will have'succesive energizing circuits completed maintaining it energized, and the circuit of magnet M closed, until wiper 25 encounters a contact 26pertaining 'to an idle switch pair. which will be. un-

grounded as shown in Fig. 1. Thereon, re-

lay R is deenergized, magnet M has its cir:

cuit opened, and the wipers 25,23,21, res main-engaging the contacts respectively, 26, 24, 22, of the idle switch pair ready to start said pair as soon as a new call is initiated over a line of the line group served by 1 their selections, a circuit for energizingthe cut-off relay 8 of line A is now first completed extending from battery B through saidrelay 8,'through contact 30-'29, ver the heavy marked conductor, through armature 43, contact 54-55, contact 62, the normal contact at 79, relay PR to battery B energizing said relay PR and relay 8." The latter, by attracting armature 10, opens the original energizing circuit and completes a locking-circuit extending through contact 2827, and to ground through normal contact40. Attracted armature 11 of relay. 8

opened the circuit of, and deenergized re lays 4. and 17, armature 12Iopened the normal battery connection to line limb'3, and armature 9, connected line limb 2 to the talking conductor connected to contact "It will be'observed that'contact 13 at the connectors has a ground maintained upon it over a branch of the maintaining circuit of t to ground at armature 40. Relay-.16 is. de-

- energized on the retractionof armature 5.

relay 8 which extends through normal contact 6 of relay 4 and attracted armature .10

As soon as relay 8 attracts .its armature's, a circuit is completed asfollowsz from bat tery B relay PR throughnormal contact at? 9, normal contact 62, c'ontact 55 54, over the upper talking conductor'to' line limb 2,

contact 9 having been closed-in time to pre vent the deenergization of relay PR already energized, as before described) over' the line limb 2, raised hook-lever1,--returning 1 over line limb 3, the lower talking conductor, through contact 56-57,'normal-contact 65, normal contact at 80, relay SR to bat-- tery B whereby relays PR and'SR? are simultaneously energized to attract. their armatures.

It should be observed that, had switch completed the selection ofan idle operatofis circuit E during the period when Switch C i was performing its. secondary travel, relays tendingover the line limbs 2+3, would be completed when-armatures3 9e42 were retractedbeforthe relays PR and SR 'could be deenergized.

Relays PR and SR having been enera gizedas soon as theswitchD completed its selecti n Whether switch Chamompletgdits' traced energizing circuit for the relays ex? I selection or not, a ground will whavebeen. placed upon the multiple contacts 53 .of the selected operators circuit E as soon as ithas selected which ground will render the circuit busy. When relays PR and SR are energized, they are not again simultaneously deenergized until the restoration to normal of switches is to be effected and the ground upon multiple contact 53 will exist throughv attracted armature 67 when relay PR is energized, or through retracted armature 67 and attracted armature 71 when relay PR is denergized and SR is energized. A further ground may be traced through wiper 52 engaging busy contact 53, normal contact 45, and relay RR to ground, the previously described ground however, :servin as a short-circuit about the winding of-R The relay 49 is provided, arranged(as for 'instance, by a copper shell disposed about BB to battery, for the purpose of-energizing the said relay RR, which is a release relay, when its-operation is desired. The slowness of the denergization of relay 49 prevents, when selection is .made, premature closing ofthe above-mentioned circuit by holding the said circuit open at the armature switch ofrelay 49 until relays PR and SR have had time to be energized over-their previously described energizing circuits.

\Vhen relays PR and SR were energized, circuit was completed fromground through attracted armatures 726S, primary offnormal spring PO", call signallamp 90 to battery, the lamp glowing and advising the operator that a call has come. in over the circuit The operator now actuates levers 9293 to connect her talking set in circuit with the calling substation A, the said talksetbeing thus bridged across the upper and lower talking conductors of circuit E,

and learns the number ofthe subscriber with whom subscriber A desires to converse. This being assumed to be-3333, the operator will actuate the buttons of the springs 5 0 d 6 in Fig. 1, Part 4, and the switch E will then transmit sets of impulses as before described. In the present case, the spring a is not actuated by the operator as the system now being described is a system employing four digits to a subscribers number only. Each set'of impulses coming over conductor 94 will cause three venergizations of relay 60 and each impulse coming over conductor 95, at the conclusion of an impulse set sent over the conductor 94, will cause the energization of relay 63. Armatures .61 and 64 ofsaid relays have makebefore-break arrangements of contact springs on .both their attractions and retractions.

The first set of three impulses trans mitted energizes relay 60 three times, wh ch relay, by actuating its armature 61, opens and closes :three timesthe circuit ,of relay PR causing it to be vdener gized and 'then energized a corresponding number of. times.

while relay PR is being -operated, asdescribed, by current through normal contact 65, the shifted off-normal contact 66, before described .asiassociated withE, to groundat 61 when 61 is attracted, .and to ground uthrough relay PR and battery B when .61

is retracted. When an impulse comes over conductor 95, .the resulting, energization of relay 63 causing it to attract and retract Relay SR however, continues energized armature 64, thus ,deenergizing relay SR by opening itscircuit atcontact 65. This does not h0wever,denerg1ze relay PR since circuit is completed therefore through normal contact 62, contact 66, contact 654164,

while relay 63 is energized. Spring 65 closes the circuit includingPR and SRtahd contact 66 before contact 64-65 is broken on the deenergization of relay 63. It willbe seen that while :the switching device E'- is transmitting these impulses, the closure of contact 66 has short-circuited the energizing circuit for relay PR and SR previously described, as extending over the line of A whereby there will be no impulse noises no ticeable in the subscribers telephone receiver at the substation. I

Each of the three deenergizations of the relay PR causes a .current impulse from ground through attracted armature 72, .nor- 7 mal contact 68, primary magnet PM to battery B said magnet then effecting three primary movements of switch wipers 96, .97, 98, bringing them adjacent to a group of terminals 130, 131, 132, of hundreds selectors H assigned for connection to the third thousandsgroup of lines including those numbered from 3,000 to 3,999 inclusive.

The first primary step of switch F shifts spring PO to put out lamp and spring PO to display supervisory signal 91 which will remain lighted until the called subscriber answers. Spring PO is also shifted to the end hereinbefore described, and spring PO is also shifted for purposes to be here-- after specified.

The deenergization of relaySR produced by energized relay 63 following the three deenergizations of relay PR causes a current flow as follows: from ground through attracted armature 69, normal contact 7 3, secondary normal contactSO, primary 'offnormal contact PO, heretofore shifted, busy relay BB to battery B which energizes said relay BR whose attracted armature 88 completes a circuit includinggenerator G and secondary magnet SM which magnet is actuated by successive impulses as long as relay BB remains energized, stepping wipers 96, 97, 98, step-by-step over the ,7 contacts 130, engaged by said wiper 96, contacts 130 of the busy hundreds selectors being characterized by a ground connection laced on them in a manner hereafter specified. Thus, relay BB will continue energized until wiper96 engages an ungrounded contact 130 when the absence of ground will deenergize relay BR, its armatures will be retracted and the further actuations of mag net SM prevented, wherebyrwipers 96, 97, 98, will remain engaging the contacts of the selected idle hundreds selector of the third thousands group. It will be observed that the wipers 97, 98, are on open circuit at armatures 86, 89 during the secondary movements of the switch, so that interference with existing conversations will be prevented. As soon as relay BB was deenergized, its armature 87, by engaging its normal contact, grounded the wiper 96, which being in engagement with contact 130 of hundreds selector H, renders the multiples of said contact at other thousands selectors F busy against such selectors seeking connection with them.

The next three deenergizations of relay PR cause current impulses to be transmitted from ground through attracted armature 72, normal contact 68, normal contact 86, contact 97131, contact SO, primary magnet PM to battery B causing three energizations of'magnet PM and three primary steps of the wipers 140, 141, 142 to select the group of contacts 143, 144, 145 formingterminals of the connectors I asi signed to the third hundreds group of the third thousands group including lines 3300 to 3399. The subsequent single deenergization of relay SR transmitted a current impulse from ground through attracted armature 69, normal contact 73, contacts 89, 98132, S0 shifted primary off-normal spring P0 busy relay BR to battery B Relay BB attracts its armature 138 to close 7 a circuit including generator G and secondary magnet SM which steps the wipers 'as hereafter explained. When an idle, that selector H were shifted on the first primary and secondary steps of such switch respectively. Armature 138 falling back grounds wiper 140 and the engaged contact 143 rendering its multiples'busy.

' The next three deenergizations of relay PR transmit three current impulses, as before described, through contact 97131, normal contact 136, contact 141144, normal contact 50", primary magnet PM to battery B energizing said magnet PM three times, which steps the wipers 165, 166, 167, around opposite the sub-group of contact sets forming terminal of lines numbered from3331 to 3339 inclusive, followed by terminal of lines 3330, zero being represented by ten impulses in automatic telephone practice. A single impulse transmitted by the subsequent deenergizing of relay SR passes-through contact 98-132, contact 139, contact 142- 145, normal contact SO shifted spring PO secondary magnet SM to battery, en-

ergizing said magnet which causes a step of the wipers 165, 166, 167 to a position one step from the edge of the contact bank, it being understood that in a connector, the position 'of the switch wipers during primary adj ust- .lected group, which are terminals of line 3333 or that of subscriber K. The secondary impulse produced upon the deenergization of relay SR foll.owingthe threevprimary impulses, willrpass through contacts 98+ 132, 142-145, alternate contact SO (contact SO engaging its alternate contact on the second secondary step of switch I) through contact 150, lower winding of test relay TR'to battery B energizing said relay. Assuming, first, that the called line is idle, in which case its multiple contact 13 will be connected to battery, as shown at L, 1

through cut-off relay 8 and will have no however, the attraction of its lower armature energized the relay 146 over a circuit which may be traced from the upper grounded armature of relay BB its contact, and through the lower armature'of relay TR to battery through relay 146, the armature 149 now looking relay 146 to ground at armature of relay RR. When, now, relay TB is deenergized, a circuit is completed from ground through relay 152, attracted arma- 'ture 148, normal contact 156, contact 16513,

armature 6 of relay 4, relay 8 to battery, relay 8 being then energized to attract armature 10 and connect the ground through contact 16513 to the multiple private con- 'tacts"28 of the line circuit of the line of K,

maybe started. The e'nergization of relay 152, as described, by armature 154 connects Armatures 159 and 164 close contact in the interrupter I through contact 160 to the" winding of relay 157 and battery, said interrupter I now alternately energizing and deenergizing the relay 157 whereby the ringing current from generator is applied to the called-for line periodically, passing through contact 16614, over limb 2, the call-bell and condenser at the substation K returning over limb 3 through contact 15-167, through lower attracted armature of relay 152 andthe inductive resistance 168 to ground through battery B whereby the bell at substation K is rung and the subscriber notified that his attention is desired.

WVhen subscriber K answers and removes his receiver from the hook-lever, a conduc tive bridge of limbs 2 and.3 is completed,

, whereby current is permitted to flow, as soon as the armature of relay 157 is retracted,

from ground through relay 151, attracted' through contact 15-167, resistance 168 to battery B energizing relay 151 whose armatures are simultaneously attracted. upper armature,by engaging its contact, completes a circuit from ground through relay 158 to battery B said relay 158then locking itself to ground through armature 161 and the upper armature of relay BB talking circuit of a connector, while armature 160 prevents further operation of relay 157 and armature 162 places an additional ground through primary ofi'-normal contact PO upon the multiple contact 143 to hold the (onnector I busy in case switch H should by means independent of the called subscriber, be disconnected from the connector The I, the release of said connector being solely controlled by the subscriber K after he has answered the call.

By the attraction of armature 164, a branch of the described circuit'extending from ground through relay 151, is completed, which branch extends through attract-ed armature .164, contacts 145142, 13298, alternatecontact 73, relay 77' to battery B thusenergizing said relay 77 whose upper armature completes an energizing circuit for relay 76, which relay, by armature 78, locks itself to ground at shifted contact PO". By make-before-break armatures 7 9 and 80, the connections ofrelays PR and SR to the limbs of the line of subscriber A are reversed, thus rendering the system available in connection with polarized register or coin control mechanisms of characters known in the art.

Subscribers A and K are now in conversation, the. talking circuit being indicated throughout the drawings by the heavily marked conductors; the transmitter of being supplied by current from'battery B through relay PR alternate contact 80, over limb 3, through impedance coil and transmitter at the substation, returning over limb 2, alternate contact 79 and to battery through relay SR while battery is supplied to the transmitter of subscriber K through an inductive resistance 168, lower attracted armature of relay 152, over limb 3, through impedance coil and transmitter at the substation,vreturning over limb 2, armature of relay 157, contact 153, relay 151 to ground.

It will be noted that the before described circuit causing lamp 91 to glow, continued uninterrupted until, on the response of the called subscriber, armature 78 was attracted; through conversation, the lamp will, of course, not glow because relay 76 is energized.

When the subscribers replace their 1 9- ceivers at the conclusion of conversation, this act on the part of subscriber K restores to normal the connector I only, while the act of subscriber A restores to normal switches C, D, F and H.

Assuming that subscriber K first replaces his receiver resulting in deenergization of relay 151, said relay, by its lower armature, closes a circuit from battery B through attracted armature 163, relay RR to ground, which relay,,by attracting its upper armature, energizes release magnet RM, which thereupon disengages the retaining pawls of the switch shafts, and the switch I is automatically restored both as to its wipers and as to its primary off-normal (PO) and secondary (SO) switch contacts, when all apparatus of the connector will be in its original position. When subscriber A replaces his receiver, relays PR and SR will, for the first time, be'simultaneously deenergized since the operators circuit, E was selected. Current V will then flow from ground at switch B, through the lower winding of relay RR, armature contact of relay 49, normal contact 15, armature of magnet RM, contact 5253, normal contacts 67, 71, through release relay BB of switch F to battery B Relay RR being energized, by its armature 82 locks itself to ground at contact P0. The armature 82 completes an energizing circuit for busy relay BR extending through contact PO to the end that said relay may be energized and wipers 97, 98, may be on open circuit while the switch is restoring. Current now flows from grounded. armature 88, through its opposed contact, through alternate contact 85, release magnet RM to battery, energizingsaid release magnet to cause the restoration of switch F. But before said magnet attracts its armature, a current impulse will have passed from battery B through attracted armature 8 1, armature of magnet RM contact 96130, contact PO", relay BB at switch H to ground energizing said relay BB which locks itself by armature at 133 through contact PO and relay BR? to battery B thus causing the relay BB to be also energized. Said relay places wipers 141, 142, on open circuit, and by attracting armature 188,1 completes a circuit from ground through said armature and its alternate contact, armature 134 and its alternate contact, release magnet RM to battery, energizing said magnet which causes'the restoration to normal of switch H, both as to its wipers and as to its primary and off-normal switch springs.

Returning now to switch D, the energization of release relay RR closes a circuit from ground through the lower armature of said relay, through alternate contact S0 secondary relay SR to battery, which relay SR is energized in order that wipers 54, 56 may be on open circuit while switch D is restoring, which the switch now does be cause release magnet RM is energized by current from battery 13 flowing through attracted upper armature of relay RR, there joining current already flowing through the upperor locking winding of said relay to ground through primary offnormal contact PO and the armature of relay PR.

relay is thereupon energized, and by its armature 37, causes the energization of secondary relay SR, while its upper armature 36, in addition to locking the relay RR, completes an energizing circuit for release magnet RM extending from ground through primary off-normal contact PO and its alternate contact and the upper armatureof relay PR. On the energization of release magnet RM, the switch C is restored to normal both as to its wipers and its primary and secondary off-normal springs, when all its apparatus will bev in its normal idle condition. i

While switch 0 is being restored, ground 1S maintamed upon grounded contact 26 at lease relay RR, so that until both switches of the pair CD are restored, and the mechanism thus made ready for use, in putting through an additional call, the contact 26 pertaining to the switch pairs will test busy to wiper 25 of master switch BB. When the wipers of switch I disengage the contactsof the line'K, circuit through the cut off relay 8 was opened and the line circuit restored to its normal condition. Similarly, when the wipers of switch C leave the contacts of the line of A, cut-ofli' relay 8 was deenerg-ized and the circuit-of the line restored to its normal position. 1

Let it be assumed that subscriber K had failed to answer the call. In such case, relay 158 would not have been energized." Thus when in consequence of'the replacing of the receiver at substation A, relay BB at' switch H operated, circuit would be completed from battery 13 extending through attracted armature 135, normal contact of armature of-magnet RM before said magnet attracted its armature, through contact 14.0, 143, shifted spring PO, normal contact 162 and through release relay RR to ground, energizing the said relay RR, which would then as before, cause the restoration of the connector In Thus, until the called subscriber answers, 'the calling subscriber controls the release-ofthe connector I as well as all the other switches. e

It will be thus seen that the work of the operator consists merely in learning the number of the called subscriber wanted and connecting out that number upon a keyboard corresponding to the lamp upon which'the call came in, and thereafter the entire operation of the system,'including the ringing up of the called-for subscriber and'the restoration of all apparatus to normal, is accom plished entirely without requiring any attention from the operator whatever.

If it be assumed that the called-for line was busy at thetime the connectorI had-its V wipers applied to the contacts of said line and its relay TR was energized'by the last secondary impulse, then the multiple contact 13'of the called-for line would have had a ground connection placed there, in case the line was busy because it was a calling line, over a connection extending (see Fig 1, Part 1) through normal contact 6, alternate contact 10,'contact 28-27 to ground through normal contact 40; or, if the line of K were busy as a called-for line, said contact 13 would be grounded over circuit extending through wiper 165 of some'other connector already engaging a multiple of said contact 13, through normalcontact 156 of said connector, through its closed contact 148, and its'relay 152 to ground. In either case of the called-for line of K being busy, relay TR, when onc'e energized, would have continued energized over a circuit extending from battery B through the upper winding of said relay TR, its attracted armature 156,

the wiper 165, and the grounded multiple 9, over limb 2, through the receiver giving the customary busy tone, returning through contacts 32-31, 5657, and to ground through normal conta'ctat 80, secondary res lay SR 'and battery 13*. Hearing the busy signal, subscriber A will replace his receiver and the entire switch mechanism, including connector I, will be automatically restored to normal, in the manner her'einbefore indi: cated.

lhe mechanism, shown inFig. 2, shows means by which the system of my invention may beemployed in connection with two exg changes located at a distance from each other, while requiring but two conductor trunks to secure the proper operation of the system. f

'The said Fig. 2 is to be placed intermediate of Fig. 1, Part 2, and Fig. 1,-Part 8, in the consideration of the trunking features, and the additional selector N being intro-. duced into the system, a system employing five digits for subscribers numbers will'be produced, there being then the first or ten thousands selector F to select the ten thousands group, the second or thousands selector N to select the thousands group, the third or hundreds selector H'to' select the hundreds tioned, T, T are the trunking conductors extending from" an exchange in which the operators circuit E is located to a distant exchange in which now the second selector N, third selector H and connector are sup po sed to be located. At M, is shown a socalled repeater circuit and at 'N', the

of a trunking secondselector.

When the trunking mechanism of Fig. 2

is used, one level of multiple contacts atfthe first selectors F will be" assigned' for""con nections to the lines in the distant'exchangeI If it'be assumed that thedistant exchange is a ten thousand line exchange, suchasthat already described as illustrated in Fig. I,

then for example, the fourth levels of the first selectors at the first exchange may have connected to them multiple ebnmcts 201,202, I

T, with the me hanism r'qyrded in Fig.2

accompanying each suchtrunk "If" the fourth levels of the first selectors area'ssigned for such'purpose, it isa'pparent that the directory numbers 1,000 to 4,999, inelusive in the first exchange must fall away .203 (Fig. 2) of two-wire'trunk circuits T,

so that the said first exchange wouldbe available in fact, but for ninethousand subscribers V In order to provide a suflicient'ly great number of trunks for the trunking can lines.

nections to be expected between the two exchanges, the multiple terminals 201, 20 2, 203;,

may, of course, be multiplied but a relatively small number of times before the wipers 96, 97, 98," of the various first selectors as com- "pared with the number of times" the,'terminals-130, 131, 132, of the local exchange,

second selectors would be multipliedf It is for trunking uses that the buttons 129'in Fig. 1, Part 4, are provided as'fivesets,v

of: digit impulses willbe usedin'trunkingconnections. In this connection 'I contemplate, where a number of ten thousand line exchanges are to be interconnected difl'er- In such case, a subscriber calling forlhis own exchange would, in the usual manner, give the prefix and number of the subscriber wanted and the operator might'be allowed to actuate the full number of five buttons, but in such case the button 129 of her own exchange would have its spring-a unprovided with means for causingit to be connected to ground when actuated by the associated button for the reason of course that but four digit set of impulses would be required to complete the connection desired.

All I distant exchange buttons 129 however,

would" have their springs a provided "with grounded opposed contacts.

It is thus seen that for local purposes, System Op r t a a We es eil e system, whereas when trunking between 129 to close contact a, and buttons 128, 127,

distant exchanges is required, the trunk calls may go through what is practically a one hundred thousand line system. As far as I am aware, such a system as that above specified wherein a selector such as F, in certain cases of. its employment, is operated as'a thousandscselector, and in other cases of employment, is used as a ten thousands selector, is novel and I shall claim this structure broadly.

To illustrate the employment of the structure shownin Fig.2, let it be assumed that the calling subscriber A calls for the subscriber K whose number will be now'assumed to be 43333, or if the subscribers are to be listed according to exchange names,

' 126,125, to close-contacts 52:0 0?, and e whereon the automatic impulse transmitter of Fig. 1, Part 4,-will proceed to transmit impulses as follows: 4, 3, 3,13, 3,, and relays 60 and 63 will operate upon relays PR and SR as hereinbefore explained. Four deenergizations of relay PR will first be effectedwhich will operate upon magnet .PM to'cause' primary movements of wipers 96,97, 98, to select the fourth group of contact sets which will comprisemultiple contacts 201, 202, 203, terminals of trunk cir- 'c'uits T, T, "The single denergization of 40- select the first idle contacts 201, 202, 203 in a manner" which will be understood from the preceding description.

Thcreafter,-three deenergizations of relay PR will occur whereby three impulses of current will :be transmitted from ground through attractedarmature 72,"retracted amarture 68, contact 86, contact 97-202, contact 205, relay PR to battery, energizing and deenergizingsaid relaythree times. Withthe first energization, armature V245 energizes releaserelay R11 which locks itself-from battery 13? through armature 244 1 and contact 201 96 toground through normal contacts84 and 87. Each energization of relay PR attracts its right-had armature to transmit an impulse of current from groundcover trunk conductor T, through contact 241, 235, relay PR to battery B in the distant exchange, which relay PR by its armature 247 transmits three impulses through contacts 227, S0 primary magnet PM to battery B, energizing said magnet PM three vtimes, which steps the wipers .220, 221, 222 of the thousands se- 7 lectors N in the distant exchange three primary steps to select a group of hundreds selectors H assigned tothe third thousands group of the distant exchange. :Primary ofi-normal contacts P0 PO PO are shifted on the first primary movement of selector N. The deenergization of relaySR following the last denergization of relay PR transmits a current impulse from ground through attracted armature 69, normal-contact'73,contacts 89, 98203, normal which relay attracts and releases its armaa ture 248 to transmit a current impulse from ground through closed contact PO, contact SO busy relay BRto battery B said armature 225 to complete a circuitfor generator G and secondary magnet SM whilev armature 224 connects relay BB through normal-contact 230 and armature of magnet.

RM with wiper 220, which wiper will enrelay then attracting its armatures 223, 226, vto place wipers 221,222, on open circuit,

gage successive contacts 130 ofhundredsselectors- H, establishing successive lockingcircuits for relay'BR .until an idle or ungrounded contact 130 is reached, when relay BR will be deenergized and itsarma turesj retracted, armature i225 preventing 7 further actuations of magnet SM, while armature 224 places a busy ground potential upon wiper 226 and the multiple contacts 130 of the selected hundreds selectorsH. relay SR thereon follows, and will cause V I the selectorF, by its wipers 96, 97, 98, to

relays PR and PR will be energized and deenergized threetimes, relay PR trans 2215-131, magnet PM to battery B operat mitting three impulses from ground througharmature 247 through contact 223, contact.

ing hundreds selectors H in precisely the same manneras described 111 connection w th:

the first system diagram. 1 a

The deenergization of relay sR following the three denergizations of relay PR will result in the energization and deenergization of relays SR and SR as before-described, relaySR now transmitting a current impulse from ground through armature 248, contact 226, contact 222132, contact SOQcontact P0 now closed, relay BR to battery B This will cause the'hundreds selector H to select the first idle connecter of i the group. a a I V It will be apparent thatthe succeeding impulse sets' transmitted from Eiwill result in the transmission of impulses through con} tacts 131-132, operating the selected con- 

